docs: def _selective_filter(self, data, indices):
          """
          Selectively filter only pixels above ``filter_threshold`` in the
          background mesh.
  
          The same pixels are filtered in both the background and
          background RMS meshes.
  
          Parameters
          ----------
          data : 2D `~numpy.ndarray`
              A 2D array of mesh values.
  
          indices : 2 tuple of int
              A tuple of the ``y`` and ``x`` indices of the pixels to
              filter.
  
          Returns
          -------
          filtered_data : 2D `~numpy.ndarray`
              The filtered 2D array of mesh values.
          """
  
          data_out = np.copy(data)
          for i, j in zip(*indices):
              yfs, xfs = self.filter_size
              hyfs, hxfs = yfs // 2, xfs // 2
              y0, y1 = max(i - hyfs, 0), min(i - hyfs + yfs, data.shape[0])
              x0, x1 = max(j - hxfs, 0), min(j - hxfs + xfs, data.shape[1])
              data_out[i, j] = np.median(data[y0:y1, x0:x1])
  
          return data_out